Vishay Micro-Measurements System 7000 Programmer’s Reference Manual
Page 41 of 142
3.14.2 Decoding the Data File
In order to maximize data transfer speed and to minimize disk space requirements, the System 7000
employs a proprietary real-time data compression algorithm on its recorded data. This data structure
provides the ability to store data using multiple recording rates. This format also reduces the size of the
raw data file by 50% or more.
Each recorded scan consists of
1 or 2 bytes of Status Information
0 to 6 bytes of Scan ID
8 to 38 bytes of Channel Data
The LabVIEW instrument driver contains a VI that implements the decoding. If you are using the
ActiveX interface or the low-level commands you must programmatically implement the decoding
process
The following sections describe the format of the compressed file data.
LabVIEW Decode Scan Data VI
Active X Programmatically implemented by user
Low-level Programmatically implemented by user
3.14.2.1 Scan ID
The Scan ID is effectively the sequence number for each scan. The Scan ID is assigned based on the scan
rate (not the recording rate). So that the first acquired scan has a Scan ID of 1, the second acquired scan
has a Scan ID of 2, and so forth. But, remember, that you do not have to record every scan so the Scan
IDs recorded to file are not always sequential. If you are only recording every 10
th
scan, the first recorded
scan has an Scan ID of 1, the second recorded scan has a Scan ID of 10, etc…
The Scan ID grows dynamically as needed.
Size Scan ID Range Max Time (at 1000 samples/sec)
16-bits 1 to 65535 65 seconds
32-bits 65536 to
4294967295
49.7 days
48-bits 4294967296 to
281474976710655
8920 years
Table 18
The Scan ID width is indicated by using 2 bits in the Status Information of each scan. The Scan ID may
be stored in absolute mode or increment mode.
Absolute Mode – The Scan ID is stored as its true value. It may be either 16, 32, or 48 bits. The
first Scan ID is always in absolute mode (as it is your starting reference).
Increment Mode – if scanner detects that the Scan IDs are being incremented by 1, no Scan ID is
stored.
If the Scan ID is stored in increment mode, the scan ID must be calculated based on the most recently
recorded scan.
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